Channeling experiments with sub-GeV electrons in flat silicon single crystals

Various planar channeling experiments, performed at the Mainz Microtron MAMI with electrons at silicon single crystals, have been reanalyzed. Two types of signals have been employed. The low energy loss signal originates from emission of channeling radiation in the energy domain between 0.4 and 9 MeV while the high energy loss signal from electrons which have lost about 50% of their primary energy by emission of bremsstrahlung photons. The (1 1 0) planar channeling data, taken at a beam energy of 855 MeV with the former signal, can well be described on the basis of the solution of the classical Fokker-Planck equation. The measurements with the latter signal at beam energies between 195 and 855 MeV indicate quantum state phenomena. For (1 1 1) planar channeling calculations with the Fokker-Planck equation have also been performed at a beam energy of 6.3 GeV. The results indicate that data taken with a crystal of 60 μm thickness [U. Wienands et al., Phys. Rev. Lett. 114, 074801 (2015)] are probably not suited to determine the predicted “asymptotic” dechanneling length of 265 μm which applies for about 48% of all electrons.